Looks like they removed the thong digitally in the second picHere are some shots (biggest resolutions I've found), quite easy to find via Google:
In my opinion, the thong picture (production still) is NOT a fake. You can clearly see the pressings from the thong on her skin. Who would spend such an effort for a Photoshop manipulation? Additionally, this picture is hosted on many movie websites.
Interestingly, in the second picture (final movie scene) nothing is visible anymore. Probably she just took that thong off or changed her underwear.
Well thongs are one of the oldest forms of clothing really. So I’d probably say they were rudimentarily invented around the time human civilization began to exist. Now the modern g-string was invented in an effort to obey a law put in place by NYC mayor LaGuardia in the 1930s that required strippers to cover their intimate parts. I guess it slowly started to catch on after thatWhen do you think thongs were invented?